1. Field of the Invention
The present invention relates to an image processing apparatus and image processing method which perform soft proof processing of reproducing, on a monitor, a print product under observation illumination.
2. Description of the Related Art
Processing of using, for example, a PC (Personal Computer), to simulate the finish quality of an actual print product obtained by, for example, a printer, and displaying an image obtained by simulation is called soft proof processing. It is a common practice in soft proof processing to perform color matching processing for color components (to be referred to as diffuse components hereinafter) of light reflected by an actual print product, and faithfully reproduce their tonalities on a display device. In the recent soft proof processing, a technique of using CG (Computer Graphics) to simulate not only diffuse components of a print product but also glossy components (illumination reflection) of the print product is becoming prevalent.
To precisely reproduce (proof) glossy components of a target print product, it is necessary to reflect its gonio-spectral reflection characteristics on soft proof processing. The gonio-spectral reflection characteristics mean herein characteristics indicating the angle and intensity of reflection of light upon irradiation, and are referred to as a BRDF (Bidirection Reflectance Distribution Function). Especially in a pigment printer that has gained a large market share in recent years, the gonio-spectral reflection characteristics change for each color because the shape of the medium surface changes in accordance with, for example, the print density and the order of ink landing. Hence, it is necessary to precisely reflect the gonio-spectral reflection characteristics of each color on soft proof processing for a pigment printer.
Conventionally, in the CG field, the glossy components are represented using, for example, a Phong model obtained by approximating the gonio-spectral reflection characteristics. Also, to more accurately reflect the gonio-spectral reflection characteristics, a technique of combining a plurality of CG models to approximate the gonio-spectral reflection characteristics of the target has also been proposed (see, for example, Japanese Patent Laid-Open No. 2004-126692).
The CG model that is conventionally introduced to represent the glossy components generates an error with respect to actual gonio-spectral reflection characteristics. This makes it impossible to precisely represent the glossy components. Also, the technique of approximating a plurality of CG models to more accurately reflect the gonio-spectral reflection characteristics of the target can more accurately reflect specific gonio-spectral reflection characteristics on soft proof processing but nonetheless cannot cope with a situation in which the gonio-spectral reflection characteristics differ for each color.